Telephone system



.lem 218, 1930. M. sxMPsoN 1,745,040

' TELEPHONE sYsTElm Filed May 12. 1928 v 8 ySheets--Sheeb l QR PsTs 5K PCR TCR Fi. Rs 'Rm RH Gs Jan. 28,1930. l.. M. SIMPSON 1,745,040,

` TELEPHONE SYSTEM Filed May 12, 192e a sheets-sheet 2 OWK l Jan. 28, 1930. M, 5|MP50N 1,745,040

TELEPHONE SYSTEM Filed May 12, 1928 8 Sheets-Sheet 5 @Mm FINI Jan. z8, 1930. L. M. SIMPSON 1,745,040

TELEPHONE SYSTEM Filed may 12, 1928 s sheets-sheet 4 UUEFLIDP- Sim scm Jn. 2s, 1930. M SIMPSON 1,745,040

TELEPHONE SYSTEM Filed May 12,' 1928 8 Sheets-Sheet 5 ETI? Jan. 28, 1930. L, M, slMPsON 1,745,040

TELEPHONE sYsTnl Filed May 12, 1.928 8 Sheevts-Sheet AFB,

TELEPHONE SYSTEM Filed May 12, 1928 a sheets-sheet 7 v Jan. 28, 1930. L. M. slMPsoN 1,745,040

TELEPHONE SYSTEI Filed may 12. 192a. a sheets-sheet e3 Y son Patented Jan. 28, 193@ UN STATES lnxraia'r l OFFICE LANoELoT MARTIN SIMPSON, oF LEEDS, ENGLAND, ASsIGNon To ASSOCIATED TELE- PHONE AND TELEGEAPH coMEANY, or KANSAS CITY, MISSOURI, A CORPORATION' OF 1DELAW'AREl i Y'.IJEIJaPIIoNE SYSTEM Application filed lviay'lZ, 1928, Serial No. 277,188, and in Great Britain May 26, v1927'.

10 only be teste-d while it is notV actually in use and must' not be busied to its normal means of access in order thata test may take place. It is generally7 recognized nowadays that routine testing is desirable, if not essential, particularly for complicated apparatus, in order thatit may be possible to anticipate faults rather than correct them'` after they occur, and for the test torbe effective it is essential that every piece of apparatusshall 20 be tested. rlhis clearly presents a diiiiculty in the above-mentioned circumstances, and it is the main object ofthe invention to deal with cases of this sortvin a simple mannenV VAccording to one feature yof the invention,

5 in an automatic testing arrangement fOr the routine testing of apparatus as used intelephone systems, in which idle pieces of similar apparatus are tested in turn until all have been dealt with, if a piece of apparatus is 0 seized for use while it is being tested, the operation of the testing equipment is suspended for an interval.

hese features and others not Specifically mentioned at this point will bebetter under- 5 stood from the following description of one method of carrying the invention into effect which should be taken in conjunction with the accompanying drawings. Clearly any routining arrangement will need to be specially designed in view of the apparatus it is desired to test and the arrangement shown has been designed for the testing of key-sending operators positions of the type described in the Passmore application, Serial No. 7 52,138

45 filed Nov. 25, 1924. It will be recalled that in the arrangement disclosed in this specification, calls passed to aB operator over an order wire are set up on a single set of digit keys the operation of which serves to control an impulse sender to send out the necessary trains .of impulses for operating automatic switches to connect with the wanted line. As a general rule the B operator will have f10 trunks incoming to her position, though lnparticular casesthis numbery may be increased to 50. Moreover, in view of the factk that the complete operation vof an impulse sender takes several times as long as the'setting of the digit keys, it iS arranged that as many as four impulse senders can be asso-` ciated with herposition at a time in order that she may work continually at full speed,

the impulse senders being accessible in corn-` mon to a considerable number of operators. The testingL of the complete apparatusfalls naturally intotwo parts, one Vcomprising the testing of the actual impulse senders which may be done as descirbed in British` Patent N o. 267606 and the other the testing of the junction relay sets andl apparatus for asso'- ciating impulse senders with the operatoris key-set, A little consideration will show that for a complete test to be carried out it is i necessaryto employ the apparatus at the operators position usedfor associating an 4idle impulse sender with that position, hence it yfollows that the test cannot be carried out while the position is in service.

Referring now tothe accompanying drawings comprising Figs. 1-8, Figures 1 and 2 show the various controlling keys and a number of the kassociated relays; Figures 3 and 4 show a further group of the lrelays controlling the routiner; Figures 5 and 6 show the test switch TS, the release timing switchRS and the number-set-up switch NS, together with the faultindicating lamps for indieating 'the vprogress of a particular test; n.

while' Figures 7 and 8 show the distribution equipment by means of which connectionis Vmade with each position in turn, and also with each junction'in turn at a particular position. In order to facilitate the understanding of the circuit, the description will be divided into two parts, firstly consideration of the arrangements by which connection is made in turn to the various positions and each junction at the position is tested, and secondly consideration of the actual tests which are carried out on the junction and the circuit arrangement by means of which they are applied.

Considering first, therefore, the distribution equipment in the arrangement shown, it is assumed that the test set is to serve for 60 operators positions and that each position has 50 incoming junctions and means for associating four impulse senders with the position at a time. The position distribution equipment comprises a primary distributor PD from which access is had to three secondary distributors SDl--SD3 of which only SD1 and SD3 are shown (Fig. 7) since the circuits of SD2 are similar. Preferably the contacts of the primary distributor PD are multiplied round the bank as shown so as to avoid unnecessary operation of the switch. Since it is not found possible to provide the secondary distributors with sufficient wipers for all the functions which they are required to perform, each one has associated with it an auxiliary secondary distributor of which only the auxiliary scecondary distributor ASD1 associated with the switch SD1 is shown in Figure 8. Each secondary distributor is wired to have access to 20 operators positions and when all the 20 have been tested or found busy, the primary distributor is advanced so as to connect up the succeeding secondary distributor. Associated with each position are a pair of junction distributors such as JD1 and JD? (Fig. 8) which are given access to a maximum of 24 and 22 junctions respectively. Where the full 50 junctions are equipped, access is obtained to the last four over the first four contacts of the distributor JDl, a suitable switching operation being performed to connect these junctions up in place of junctions 1-4 as will be described subsequently. The junction distributors are provided with a normal position in which the contacts are left dead and by this means the wipers of the junction distributors associated with all the positions may be multiplied together to the routine test set and the position distributors ensure that the junction distributors of only one position shall be operated at al time.. It should be mentioned with reference to Figure 7 that the banks of wipers 618 620 of the secondary distributor SD3 are wired to the various junction distributors in the same manner as is indicated by the wiring of the first contacts in the banks of secondary distributor SD. The bank of wiper 617 is wired to the contacts of the associated position battery feed relays while that of wiper 621 is wired to the bank of the associated auxiliar secondary distributor ASD3. The switch Dl is wired similarly. As regards the auxiliary secondary distributor ASD1, over Wipers 639 and 640 of this switch access is had to the order wire leads of the various positions, while over wipers 641-644 connections are made to the four leads extending from the o erators keyset so that a test number may be set up from the routiner. Over wiper 645 circuits are completed for changing over from junctions 1 4 to junctions 4750 where this is necessary. The other auxiliary secondary distributors are wired in a similar manner. The bank of wiper 625 of the junction distributor JD1 is wired to the lamp leads of the various junctions, that of wiper 626 to the respective assignment leads and those of wipers 627 and 628 to the negative and positive trunk conductors respectively. The banks of the wipers such as 629 of all the junction distributors are commoned together and extend to indicating lamps such, as 648 by means of which the attendant may see whic 1 junction is being dealt with at any time. The particular position being routined is indicated by the lighting of the correspond- Y i ing lamp such as 608 connected to the banks of wipers 612 and 618. These lamps will fiash as described subsequently when the associated position is being tested and will glow steadily when the routine indicating key is operated if the position has been tested or the busying key G09 is operated.

T he operations involved in making a test will now be considered in detail. In order to set the routiner in operation, the attendant operates the stait key SK whereupon a circuit is completed for relay 115. Relay 115 upon operating, at armature 116 prepares a circuit for the test relay 131, at armature 117 completes a circuit for the relay 119, and at armature 118 prepares the pulsing circuit to the first secondary distributor. Relay 119 now operates and at armature 120 opens the circuit of relay 28() which is normally energized in the following circuit: battery, relay 280, lead 407, normal contact and wiper 622 of the switch SD, normal contact and wiper of the switch SD2 represented by the link 624, normal Contact and wiper 616 of the switch SDl, lead 18, armature 120 and its back contact to earth, and at the front contact of armature 120 extends earth over lead 26, wiper 603 of the primary distrilfmtor PD, lead 23, winding of relay 215 to battery so that relay 215 is operated and prepares circuits for the junction distributors and auxiliary secondary distributor and also for the relay 185. Furthermore, at armature 121 relay 119 prepares a circuit for stepping the junction distributors, and at armature 122 completes a circuit for relay 127 which extends as follows: battery, winding of magnet 507 of the switch TS. lead 43E), armature 313 and its back contact, lead 441, interrupter contacts 508, wiper 506 and its normal contact, lead 93, winding of relay 127. armature 122 and its front contact. lead 43, back contact and armature 332 to earth. Relay 127 is operated at this time and at armature 128 opens a point in the locking circuit of relay 112, at armature 129 prepares circuits for relays 152 and 180 and at armature 130 closes the pulsing circuit of' the secondary distributor, Relay 119 'moreover at armature 123 opens the homing circuit of the primary distributor and provides a lockingl earth, at armature 124 prepares a circuit for stepping the primary distributor after each secondary distibutor has rotated over all positions connected to it, at armature 126 opens an alarm circuit over lead 57 Vand at armature 125 connects earth to Viiiotonstart lead 494 and opens normally closed circuit for relay 278 which extends as follows: battery, Winding of relay 278, lead 493, link 649 representing wipers and normal contacts of all the j un-ction Vdistributors not shown, normal contact and wiper 637, normalcontact and wiper 630, lead 1, back Contact and armature 125 Vto earth. Relay 278 now de-energizes thereby altering certain supervisory,circuits as will be described subsequently. The pulsing cir-V cuit completed on the operation of relay 127 Yao extends from earth, winding `Yof relay 264, armature 267 and its back contact, lead 47, armature 148 and its back Contact, lead 61, back contact and armature 2686, lead '62, armature 136 and its back contact', armature 118 and its front Contact, front contact and arinatureh130, lead 50, backV contact and armature 271, lead V51, armature 153 and its Vback Contact, armature 167 and its back contact, lead 27, wiper 605 of the primary distributorand the first contact in its bank, winding of magnet 610 of the secondary distributor SDl, lead 29, winding of relay 233 to battery.YV ln this circuit the battery feed relay 233 is'operated and at armature 234'completes a supervisory circuit which will be more fully described later. `Moreover magnet 610 is operatedand at tracts its armature preparatory to advancing the Wipers of the switchy SDl and relay 264 isalso operated and at armature 265 completes a circuit for relay 268. This relay at armature 269 completes a Vcircuit for the slow` to-pulluprelay 266 which upon operating in due course, at armature 267 opens the circuit originally traced, whereupon relay 264 and magnet 610 fall back and the latter v advances the switch SDl one step. Relay 264 upon releasing, opens'the circuit of relay 268 and this in turn brings down relay 266` whereupon, unless the operators position then connected with is in conditionr to be tested, magnet 610is again energized and the cycle re-commences. The relay 533 in Fig. 6 is used for feeding battery to theoperators headset and when the operator is absent from the position and has therefore Withdrawn her headset plug, relay 533 is deenergized and extends earth over armature 534 and lead 408 to the first contact in the bank of the secondary distributor SDl over which access is obtained to this position. It

will be understood thatthe battery feed relay ofthe other operators positions are ,connect ed up similarly to other contacts in the banks of the switches SlT-SDE. rlhe secondary distributor continues to advance step-by-step ture`160, back Contact and armature 1,45, armature 116 and its front contact, windingY of y relay 131,l lead 56, low resistance upper windiiig of relay 276, armature 277 and itsback contact to battery. Relay 131 is operated in this circuit but not relay 276 in normal working, and the former at armature 132 opens Ya point in the circuit of relay 270, at armature 133 prepares .a circuit for the Amagnet 631 ofY thejunction distributor J D1, at armature 134 completes a circuit fory relays 109 and152, at armature V135 closes another point in the circuit of relay and at armature 136 disf connects the pulsing earth from the magnet of the secondary distributor SD1V and extends it to tlieinag'net of the auxiliary secondary distributor ASDl over frontcontact and armature 218, armature'191 and its back contact, klead 2, magnet 647, lead650, lead 29 to battery through relay 233,. Consequently the auxiliary secondary distributor now commences to step and this continues until relay is energized when the auxiliarv secondar i i3 Y u istributor reachesthe same position as its associated secondary distributor. The circuit for relay 185 may be traced from earth, Wiper 604 and its first contact, ywiper 615, Contact in bank corresponding to position of wiper 615, corresponding connecting wire of banks of wipers 615 and 646, vto wiper 646, lead 3, armature 219 and its front contact, winding of relay 185 to battery, and the operation of the relay opens the stepping circuit at armature 191. When relay 152 operates, at armature 153 it opens another point in the pulsing cir-x cuit to the secondary distributor, at armature 154v prepares a circuit for flashing the indicating lamp by means of relay 274, at ar- 373 mature 155 completes a klocking circuitk for itself which extends as follows: battery, winding ofrelay 152. armature 155 and its front contact, normally closed right hand springs of the re-start key RS, armature 169 and its back contact, front contact and armature 123 to earth, at armature 156 opens a point in the circuits of the relays 137, 143

and 162, at armature 157 prepares a circuit for homing the junction distributors, and at armature 158 connects earth from interrupter 92 over lead 54 to relay 274 to flash the position indicating lamp. The operation of relay 185 also at armatures 186-189 and 192 and 193 prepares the connection of the digit and order wire leads over leads 79-82 and 9 and 10 to the wipers of the auxiliary secondary distributor, and at armature 190 completes a circuit for relay 180 extending as iollows: battery, winding of relay 180, lead 651, arn'iature 113 and its back contact, lead 652, front contact and armature 190, lead 653, front contact and armature 135, armature 129 and its front contact, front contact and armature 134, armature 169 and its baci; contact, front contact and armature 123 to earth. Relay 180 upon operating, at armature 181 completes a circuit for relay 229 and this locks up by Way ot armature 230, at armature 182 completes the following circuit for relay 330: battery, windingl of relay 330, lead 45, armature 182 and its front contact, lead 33, wiper 502 of the switch T S and the tirst contact in its bank, lead 453 and by way oi interrupter 485 to earth. Moreover at arn'iature 183 earth is connected over lead 4, armature 331 and its back'contact, lead 654, upper winding of supervisory relay 314 to battery, and at armature 184 the homing circuit of the test switch TS is opened and earth is connected to wipers 501 and 503. Then the contacts of interrupter 485 next close, relay 33 is operated and at armature 331 opens the circuit of the relay 314, at armature opens the circuit of relay 127 and completes a direct circuit for magnet 507 and at armature 333 completes a locking circuit for itself extending as follows: earth, armature 332 and its front contact, lead 441, interrupter contacts 508, lead 429,.armature and its back contact, armature 333 and its front contact, winding of relay 330 to battery. The connection of earth to wiper 501 completes a circuit for the first supervisory lamp 542 which lights to indicate that a free position has been found. Vhen magnet 507 has operated fully and opened interruptor contacts 508, relay 330 cle-energizes thereby opening the circuit of magnet 507 so that the switch TS is advanced one step. The earth connected to Wiper 503 is now extended over lead 440, lead 35, back contact and armature 163, armature 121 and its front contact, front contact and armature 133, lead 655, armature 176 and its back contact, armature 216 and its front contact, lead 20, wiper 613 and the iirst contact in its bank, lead 656, magnet 631 of the junction distributor JDl, lead 402, winding o't supervsory relay 295 to battery so that magnet 631 is operated. The succeeding pulse from interrupter 485 again operates relay 330 and this in turn eifects the advance of the test switch. When the test switch takes its next step and advances to its third position, the circuit just traced is opened and accordingly the Wipers of the junction distributor JD1 are advanced one step. In case the position which has been connected with should only just have been vacated by the operator so that there is a call still in progress over the tirst junction, there will be earth on the lamp lead and this will accordingly be extended over the appropriate contact in the bank of wiper 625, lead 13, normally closed springs of the fault imitation key 84, lead 74, armature 340 and its back contact, lead 657, upper winding of relay 376 to battery. Moreover owing to the advance ot the test switch, the initial circuit over lead 440 is opened and relay 334 is operated over wiper 503 and lead 443. Accordingly the following circuit is now completed: earth, relay 264, armature 267 and its back contact, lead 658, armature 379 and its front contact, lead 659, armature 335 and its front contact, lead 35 and thence over the circuit previously traced to the magnet of the junction distributor J D1. Consequently this switch is again operated and if one or more further busy junctions are encountered, relav 376 remains operated so that the movement continues until the switch .TD1 has been moved into engagement with a junction over which no call is in progress. Relay 376 will then cle-energize and complete a circuit for advancing the test switch which now continues its operation and applies the various tests in turn to this junction as will be fully described subsequently.

Vhen wiper 503 has made a complete revolution and again comes into engagement with the second contact in its bank, the circuit traced above again becomes operative for advancing the junction distributor, and in the ordinary course this will take only one step and the next junction will then be connected up for testing purposes. In case, however, this junction should still be in use or should be out of service for any reason, there will be earth on the lamp lead and this will operate relay 376 to step the junction distributor on past this junction as above described.

As already pointed out, the switch .TD1 is arranged to deal with 24 junctions, and when its wipers are advanced into engagement with the last of these junctions, the following circuit is completed: earth, wiper 629 and the 24th contact in its bank, lead 12, winding of relay 172 to battery. Relay 172 upon operating. at armature 173 shunts armature 176 and its back contact and at armature 174 completes a circuit for relay 175. The latter upon operating, at armature 178 locks to earth at armature 123, at armature 17 6 prepares a circuit for the magnet 638 of the junction distributor JD2, at armature 177 prepares a circuit for relay 270 and at armature 179 prepares an auxiliary circuit for the magnet of the junction distributor JD2. Vhen the testing of this junction has been completed and the test switch again reaches position 2, earth is again connected to lead 440 andv isfeXtended to the magnets of both distributors JDl` yand JD2, hence JD1 is advanced to its 25th or nor-y mal contact and JD2 takes one ystep and .tests the first junction in `its bank. When the switch JD1 steps, the circuit of relay 172 is opened and thereupon releases and prevents any further pulses being sent to magnet 631. It the first junction in the bank of JD2 is idle and in service the usual tests are carried out thereon and the switch JDZ'is'advanced one step to connect up a succeeding junction.

When all the junctions accessible from the bank ofthe switch JD2 have been tested, the switch wipers will be advanced to position 23 whereupon a circuit is completed kas follows: earth, wiper 636 and the .23rd Contactin its bank, lead 11, winding of relay 166 to battery. Relay 166 upon operating, at armature 167 opens a point in the circuit lor steppingthe secondary distributor, at armature 168 opens a point in the circuit of relay 270, at armature 169 opens the circuit of relays 109, 152, 175 and 180, at armature 170 closes a point in the circuit of relay 285 and at armature 171 completes a circuit for stepping the junction distributor JD2 a-urther step. When relay, 180 de-energizes, earth is supplied at armature 184 for homing the test switch and when this reachesnormal position, relay 127 is operated... Relay 175 being slow to releaseholds up for a moment and when it de-energizes the wipers of the switch JD2 are advanced a further step and the circuit rof relay 166 is then opened and it slowly releases. With the wipers of JD2 in the 24th position, the following circuit is completed: earth, wiper 636 and the 24th contact in its bank, lead'670, irst contact inthe :bank of wiper 612 and said wiper, iirst contact in the bank of wiper' 602 and said Wiper, lead 25,armature 154 and its backcontact to the lower terminal'of the winding of relay 131. Since the original earth connection to the other terminal of this winding is still intact, relay 131 is lnow short-circuited and accordingly defenergizes, thereupon at armature 13.6 again connecting up thegpulsing circuit from relay 264 for advancing the secondary distributor. Accord ingly conditions are now similar to' those obtainedl when the test was started and the secondary distributor SD1 hunts to find an idle position. vWhen such a position is found as indicated by the presence of earth on the associated contact in the bank of wiper 611, relay 131 again operates and at armature 136 cpmpletes the circuit for advancing the auxiliary secondary distributor correspondingly.v The appropriate junction distributor is then advan'cedv one step and it necessary hunts to nd anidle junction 0n which tests are made as before. j

lVhen all the positions accessible from the sec-ondary distributor SD1 havek been j tested or found busy,'.wiper 615 willbe engaging the f 21st Contact in its bank and al circuit will then be completed as follows: earth, wiper 604 and the first contact in its bank, wiper 615 and thef2'1st contact in its bank, lead 403, winding 4of relayy297 to battery. Upon the operation of relay 297 a circuit is completed from earth, armature 124 and. its frontcontact, lead 69, armature 298 and its front Contact, lead 68, winding ofmagnet 607 of the pri- `mary distributor, lead 2,9, winding of relay 233 to battery as before. Magnet 607 thereupon energizesbut does vnot yet advance its Vassoci ated wipers Since relay 131 is still not operated, a circuit is again completed for advancing the secondary distributor SDl, and wiper 615 accordingly leaves its 21st contact.` Consequentlyy the circuit for .relayv 297 j is nowopenedjandit releases, `thereby opening the circuit forfthe magnetf607 of the primary distributor whichv advances .the

wipers one step. The secondary distributor SD2 is thus connected up and the positions accessible over its bank are then tested in the.

manner previously described. When it far# rives vat position 21, a circuit is completedr for advancing the primary distributor in the same way as above described, and accordingly the secondary distributor SD3 is brought into action and the unstaded ypositions, accessible from its banks are dulytested. When all thesey positions have been dealt with, wiper 621 engages the `21st Contactin its bank land a circuit isthen prepared for relay 285 but this is notfcompletedowing to the fact that it isheldkopen at armature 231, relayf229 being operatedat this time. Consequently the switch SDafcontinues to step in response to pulses from relay 264`l'until 'it engages its 23rd Contact whereupon a circuit is completed ioo from earth on wiper 604 as before, lead 401,k

winding of relay 292 to battery. Relayy 292 upon operatingat armature 293 opens the locking circuit of relay 229 thus causing it to release and at armature 294 extends earth therefore provided in the presentfinstance that after all positions have been tested once for busy oridle condition and the idle ones.

duly routined, the various positions are again tested, only on this occasionn'ot only `posi- 4110 from'lead 69 over lead 68 to the magnet 607 of the primary distributor and this is accord- Vto test all the operatorsr positions. It is v1,25

tions which are actually busy have to be passed over but also those which have been routined on the previous operation of the distributing switches. The necessary discrimination is effected due to the position which the second junction distributor takes up when a position has been completely routined. Reference to Figs. 7 and 8 will show that in this case earth is applied over the 24th contact in the bank of wiper 636 of the junction distributor JD2 to the contact as- Vsociated with the position in the bank of wiper 612 and this will have the effect of roducing a short circuit on relay 131, so that in the case of positions actually in use no earth is supplied to this relay and in the case of positions which are not in use but which have already been tested earth is supplied to both terminals of the relay so that in either event the relay is unable to operate. Accordingly it does'not open the pulsing circuit to the secondary distributor and this switch steps over the position. It will be recalled that when a free position is encountered, relay 131 operates and completes a circuit for relay 180 and this in turn operates relay 229 which locks up dependent upon relays 280 and 292. Hence if all the secondary distributors should pass over the whole of their banks without finding any position in a condition to be tested, relays 131, 180 and 9.29 will not be operated and in this case when wiper 621 of the secondary distributor SD3 engages its 21st contact, earth is extended over lead 15, armature 231 and is back Contact, lead 65, upper winding of relay 285 to battery. Relay 285 is a two-step relay and at this time only operates its light armature 290 thereby short-circuiting its lower winding by earth on the lefthand contacts of the restart key RS. Then the secondary distributor SD3 recives a further pulse, the initial energizing earth is removed and relay 285 then operates fully over both its windings in series and is accordingly locked up to the re-start key RS. The operation of relay 285 at armature 291 completes a circuit for the routine finished lamp 284 and the lower winding of relay 314 in series and relay 314 operates with results to be described subsequently. Relay 289 moreover at armature 286 opens the normal pulsing circuit for the secondary distributors and auxiliary second ary distributors, at armature Q88 opens an auxiliary energizingT circuit for itself, at armature 289 opens a point in the circuit of relay 131 and at armature 2ST connects earth to wiper 616 of secondary distributor SDH This switch accordingly commences homing and when it has reached its normal position the homing earth is extended to the secondary distributor SD2. ihen this switch in turn has reached its normal position the homing earth is transferred to the switch SD3 and when this switch has returned to normal a circuit is again completed over lead 407 for relay 280. Relay 280 upon operating, at armature 281 opens a further point in the locking circuit of relay 229 and at armature 282 opens a point in the magnet alarm circuit.

In case the attendant discovers by operat ing the key RIK as described subsequently that a number of positions have still not been tested, he may leave the routining apparatus in this condition for an intervaland thenby operating the re-start key RS, again set it tohunt for and routine positions which have not yet been dealt with. 1V hen the re-start key is pressed, the locking circuit for relay 285 is opened and it releases thereby completing the pulsing circuit for the distributor SDR The operation now proceeds as before and continues until all three distributors again make a complete rotation without finding any position in condition to be tested. lt will be noted that in these circumstances only the secondary distributors are restored to normal but not the junction distributors, since these switches indicate by their off-normal position that the associated position has already been 4 the distributor SD1 whence it is extended in turn to distributors SD2 and SD3. Over armature 123 and its back contact earth is applied over lead 28 to the bank of wiper 606 so that this is effective in bringing about the homing motion off the primary distributor. The earth over the back contact of armature 125 is extended over lead 1 to wiper (3230 of the junction distributor JD1 and serves to effect the homing motion of this switch. lhen the switch reaches its normal position, the homing earth is extended to the switch JD2 and this in turn is operated to normal. All the other junction distributors accessible to the routiner are homed in a similar manner, one after the other, and accordingly all the apparatus is left in the position shown ready for a further test to be initiated, for instance the next day. The sole exception is the auxiliary secondary distributors for since they always follow their associated secondary dis- 285, but this could if desired be dependent on relay so that it would release When the start key was restored.

Consideration may now be given to the actual tests which are made on each junction. The initial circuit for stepping the test switch Ts has already been traced, uns being completed owing tothe operation of relay 330 when relay 180 is energized. It was pointed out, moreover, that with the test switch engaging its second set of bank contacts, a. circuit is completed over lead 440 for advancing the first unction distributor of the seized position one step, the test switch meanwhile moving to engage its third set of contacts. j In case the junction which is thenconnected with should have a call in progress or should be out of service, there will be earth on the lamp lead and accordingly the junction distributor will again be advanced under the joint control of relays 334 and 376. l/Vhen relay 376 deenergizes, a circuit is completed for relay 330 extending as follows: battery,`winding of relay 330, lead 45, armature 182 and its front contact, lead 33, wiper 502 and the third contact in its bank, lead 461, back contact and armature 382, lead 671, interrupter 485to earth, so that the switch TS is moved to fourth position. In this position a circuit is completed over the fourth contact in the bank of wiper 503 and lead 446 for relay 336; Upon the operation of relay 336, earth through the lower winding of relay 376y is connected over lead 672, front contact and armature 340, lead 74, normally closed springs of the lamp lead disconnect key 84, lead 13 and over wiper 625 of the Yswitch JD1 to the lamp lead; if this lead is continuous, battery through the lamp will be operative to energize relay 376. Moreover at armature 337 earth is connected through the winding of relay 389 and over lead 405 and wiper 628 to the positive trunk conductor. In case this trunk shouldV be in contact with any adjacent leads, a circuit will now be complete-d for relay 389 'and it will thereupon operate. Furthermore, at f armatures 338 and 339 the windings of relay 385 are connected together and over lead 404 and wiper 627 to the negative trunk conductor. The windings of relay 385 are connected in opposition so that if there is no potential on the negativel conductor at this'tiine, the relay will not operate but in case the negative vline should be in contact with some adjacent leads, relay 385 will be unbalanced and will therefore operate. The condition for a successful test is therefore that relay 376 should be operated but that relays 385 and 389 should not be operated. 'In'these circumstances no circuit is completed for the `fault indicating lamps 538-540 which"r are wired to the fourth position of the test switch. It will be seen however thatif relay 376 fails to energize, earth on lead 437 will be extended over back contact and armature 378, lead 438,- lamp 538,

vlead 476 and lower winding of relayf314 to battery. y,Similarly if relayV 385y operates a circuit is completed over front contact and armature 386 and lead 436 for lamp'539 and if relay 389 operates lamp 540 is lighted over armature 390 and lead 435. A circuit is now completed from the interrupter 485, lead 671, front contact and armature 383, back Contact and armature 387, armature 391 and its back Contact, lead 462, fourth contact in the bank of wiper 502 and said wiper, lead 33, front contact and armature 182, lead 45, winding of relay 330 to battery. Relay 330 is accord ingly operated and effects the advanceof the test switch yin the manner previouslyv described. With the test'switch in 5th position a circuit is completed over lead 427, wiper 503 and lead 447 for relay 341; Upon the operation of relay 341, battery through resistance 399 is connected at armature 342 over lead 673 through relay 389 to the posi tive trunk conductor and atA armature 343 earth through the lower winding of relay 385 and over lead 674 is connected to the nega'- tive trunk conductor. Relay 385onlyfoperates if there is battery onthe negative line, while the resistance of relay 389 and resistance 399 in series is sufficiently high to prevent the operation of two line relays in parallel iftwo positive lines should be in contact, but will allow one line relay to operate if there is no contact. Relay 389 is also now operated and the conditions set up by thisy test are equivalent to the taking of the junction by an A operator before it has beenassigned. Accordingly if the junction line rew lay has duly energized, the correct operation at this time is that the junction lamp should be caused to flicker.y Hence since relay 336 released when the test switch moved t-o fifth position .the flicker pulses connected 'to the lamp lead are now transmitted over armature 340 and its back contact to the upper winding of relay 376. Each time relay 376 operatesr in response to the flicker the following circuit is completed: earth, armature 392 and its front contact, armature 388 and its back Contact, armature 384 and is front contact,

lead 464, miultipled contacts 5, 6 and 7 in the bank of wiper 502, lead 33, front contact and.'

armature 182, lead 44, winding of relay 330 to battery. rlihe operation of relay 330 as before effects the stepping of the' test switch over the next three4 positions. these positions earth over wiper 501 is eX- tended to the indicating lamp 543. i

tion, the circuit of relay 341 is opened and earth is connected over wiper 501 and the inultipled 8th, 9th, 10th and 11th contacts in its bank to the junction assigned indicating lamp 544. The stepping` of the test switch over the 8th and 9th contacts is effected by earth from the interrupter 485 being extended over armature 400 and its back contact and lead 454 to the contacts engaged by wipery 502 whence a circuit is'completed for 'relay 330 in the usual manner. switch yis in its ninth position, a circuit iscompleted from earth on wiper 503 to the ninth contact in its bank, lead 444, lead 406 In each" of Y kWhen the test switch reaches its 8th posi- IVhile the test and wiper 626 to the assignment lead associated with the junction. Accordingly the junction is assigned and the sence' linder and junction finder at the operator-s position are thereupon started up. Since both relays 336 and 341 are now de-energized, both relays 385 and 389 are disconnected and the upper Winding of relay 376 is connected as before to the larnp lead. Then the sender finder and the junction tinder complete their operation, a flash is applied to the lamp, consequently relay 376 will now pulse in syncbronisin with this flash. Upon each operation of relay 376, earth is connected at armature 377 to lead 434 whence it is extended to the 11th contact in the bank of wiper 502 and serves to operate relay 330 as before. lVhen the test switch reaches position 12, indicating lamp 545 is lighted and a circuit is completed ver wiper 503 and lead 448 for relay 344 which accordingly operates. Thereupon at armatures 348-351 it connects wipers of the number-set-up switch NS by way of leads 449452, leads 79h82, armatures 186-189 and leads 8 to wipers 641-644 of the auxiliary secondary distributor ASD1 and at armature 345 completes the following circuit: earth, winding of relay 264, armature 267 and its back contact, armature 345 and it-s front contact, lead 470, first contact in the bank of Wiper 530 and said wiper, winding of magnet 531 to battery. Moreover at armatures 346 and 347 it opens the homing circuit of the number-set-up switch and at the former armature connects the conimoning of contacts 2-16 to the pulsingr lead from relay 264. Relays 264, 266 and 268 now interact in the malmer previously described to send impulses and the switch NS is thus stepped round to etl'ect the setting up ot' the digit storage relays in the impulse sender, this corresponding to the operation of the digit keys by the operator. It will be understood that the appropriate contacts in the banks of wipers 528 ot the number-set-up switch are suitably jumpered to earth so as to effect the setting up of the test number which will secure that the test call is routed back to the routiner in a manner which will be more fully described subsequently. lVhen the switch N S reaches its 16th position after having set up a full 7-digit number, a circuit is completed from earth on the 16th contact in the bank of wiper 529, lead 675, 12th contact in the bank of wiper 504, interrupter springs 508, lead 441, back contact and armature 313, lead 439, magnet 507 to battery. Accordingly the magnet is energized and since the above traced circuit includes the interruptor contacts 508, the test switch is advanced one step into the 13th position. In this position the circuit of relay 344 is broken and it de-energizes, thus disconnecting the wipers of the number-set-up switch and completing circuits t0 cause this to return to normal under the control of interrupter contacts 532. In the 13th position of the test switch indicating lamp 546 is lighted and a circuit is completed over Wiper 503 and lead 456 for relay 352 which upon operating, at armature 356 locks to earth provided at armature 184 ot the relay 180. Moreover at armature 354 it connects battery through resistance 399 and relay 389 to the negative trunk conductor and at armature 355 connects earth through the lower winding of relay 385 to the positive trunk conductor. This corresponds to the taking of the junction line by the A operator and causes the starting of the sender.

The code digits set up on the storage relay groups in the impulse sender in response to the operation of the number-setup switch are now sent out, suitably translated so as to cause the routing of the call over a special test level in a selector whence connection is established back to the routiner over the leads 481, 482 and 483. lVhen switching through is eected at the selector, a circuit is completed for relay 367 which extends as follows: from battery, lower winding of relay 367, normally closed springs controlled by armature 359, lead 482, negative trunk conictor, polarized relay in the junction relay 's t, positive trunk conductor, lead 483, armature 363 and its back contact, normally closed springs controlled by armature 358, upper winding ot relay 367 to earth. Relay 367 is accordingly now operated but the polarized relay in the junction relay set does not operate at this time owing to the current flow being in the wrong direction. Upon the operation of relay 367, at armature 368 a circuit is prepared for relay 364 and at armature 369 a circuit is completed i'or relay 370 and this accordingly operates in turn and at armature 371 prepares a circuit for relay 309. After the junction has been assigned, a steady earth should be applied to the lamp lead and it' this condition is duly fulfilled, relay 376 will be held energized over its upper winding. In case, however, any irregularity should have occurred so that flash or fiicker pulses are still heilig applied to the lamp lead, relay 376 will rie-energize and will thereupon complete a circuit for relay 309 which locks up and gives the alarm as will be described subsequently. Relay 370 also at armature 372 prepares a circuit iior relay 374, while at armature 373 relay 304 is connected to the test conductor 481 extending from the selector level Yfor a purpose which will be described subsequently.

The sending of the numerical digits from the sender will now be initiated and accordingly relay 367 will pulse in response thereto, on each cle-energization completing a circuit for relay 374 which owing to its slow characterstic holds up throughout the train. Thereupon at armature 375 earth is connected to the 13th contact in the bank of wiper 502 and when this is removed at the end of the train of impulses the test switch is advanced one step in the usual manner to the de-energized, at armature 305 and *its back contact earth is applied to the 14th, 15th and 16th contacts in the bank of wiperk 502 over armature 375 and accordingly the test switch is advanced through these positions as the various digits are received. When the test switch is advanced to its 14th position after the reception of the iirst numerical digit, a circuit is completed from the earth on wiper .503 and over lead 460 for relay 357 andthis upon operating, at armatures 358 and 359 disconnects relay 367 and connects up in its place relay 523. The battery and earth connections now made to the lines are opposite to those supplied by relay 367 and this is accordingly a test for reversalof the outgoing lines. The operation of relay 523 completes a circuit from'earth through the winding of relay 521, armature 524 and its front contact, lead 475, lower winding of relay 367 to 'battery so that relay 367 is held at this time and accordingly relay 370 also. Impulses now received will therefore cause relay 523 to i pulse and the pulses will be repeated atarmature 524 to relay 367. This operation only takes place for the reception ofthe second numerical digit and when this hasbeen successfully completed', the test switch is stepped so that relay 357 is no longer energized. The third and fourth numerical digits are then received in a similar manner and the test switch is accordingly stepped to its 17th position. In this position indicating lamp 548 is lighted and the earth on lead 427 is also extended over wiper 503 and lead 465 to relay 360. The operation ofv relay 360 at armature 363 connects busyash battery from lead 480 to the positive lead from the selectorv and at armature 362 connects battery to the earthed winding of relay 367 for the purpose of holding this relay. Moreover at armature 361 contacts 331 of relay 330 are short-circuited so as to prevent undue delay in the operation of the alarm owingto the fact that this test is prolonged for three pulses of busy flash. 4The application of'busy flash battery over the positive lead should result in the repeating back of a corresponding connection from the junction relay set, that is to say the connection of battery to the lead coming into the routiner over wiper 627 of the junction distributor JDl. Hence since relay 352 is still locked up and therefore armature 355 is operated, a circuit isnow completed for the lower winding of qrelay 385. Upon ther operation of relay 385, at armature 388 a circuit is completed over wiper 502 of the test switchl for relay 330y and when relay 385 releases, this circuit is broken and accordingly vthe test switch is stepped. In this manner it moves a further three steps and thus advances into its 20th position. A circuit is now completed for indicating lamp 549 and also from earth on'wiper 503, by way ofthe 20th cony tact in its bank, lead 458, front contact and armature 368 and winding of relay 357 to battery. The operation of relay 357 as before disconnects the windings of relay 367 and connects -up instead the windings of relay k523 which are reversed in polarity. Accordingly the polarized relay in the junction relay set should now operate and connect .up battery to the negative lead in order to give answering supervision to the originating A operator.

means of which the shunt and series resistance n of the circuit may be altered so as to test the operation of the polarized relay Vwith various limits Yfor the junction resistance. The operation of the polarized relay by connecting battery to the negative lead effects the operation of relay 385 and this as before operates armature 388 though in this case earth is extended over. lead 463 to the 20th contact in the bank of wiper 504 and thence over the in-` terrupter contacts 508, lead 441, back contact and armature 313, lead 439, winding of magnet 507 kto battery. Accordinglyjmagnet 507 operates land breaks its own circuit at contacts 508 and thus advances the wipers of the test'switch into the 21st position whereupon indicating lamp 550 lights. The earth on wiper 503 is now extended over lead 459, winding of relay 364, front contact and armature 368, winding of relay 357 `to battery whereupon relayy 364 operates and relay 357 As before relay 523 at armature 524. completes a holding circuit for relay 367 generator G by wayof lead 676, armature 325 Y and its back Contact to thev positive lead 483 whence it is extended over the selectors used and through the condenser in the talking circuit tothe corresponding contact inl the `bank of wiper 628 of the junction distributor J D1, lead 405, back contactand armature 324, condenser 484, lead 677, armature 365 and its front contact, lead 678, windingof alternating current relay 393 to earth. If the talking condenser is in proper condition, the ringing current thus transmitted is suiiicient to causethe operation of relay 393 and this at armaturek 394 completes a circuitfor relay 328 whichy at armature 329 in turn energizes relay 326. The operation of armature 327 whichthen takes place is leective to energize the two-step relay 321 through its tirst step, whereupon it prepares a locking circuit for itself to lead 69 at armature 322. At the end of the ringing current period, relay 393 releases and accordingly relay 328 and after a short interval relay 326 also releases. Thereupon both windings of relay 321 are connected in series and it operates t'ully thus at armature 323 opening its own initial energizing circuit and at armatures 324 and 325 transferring the ringing current connection to the negative lead. A circuit may be now traced as follows: earth, generator G, front Contact and armature 366, lead 676, armature 325 and its front contact, lead 679, negative conductor 482, through the selectors and the condenser in the negative conductor of the junction relay set, wiper 627 of the junction distributor J D1, lead 404, front contact and armature 324, condenser 484, lead 677, armature 365 and its front contact, lead 678, winding of relay 393 to battery. Then the next period of ringing current starts, relay 393 is again operated and operates relays 328 and 326 as before. Owing to the operation ot relay 321 however a circuit is now completed as follows: earth, armature 327 and its front Contact, armature and its front contact, lead 477, 21st contact in the bank of wiper 502 and thence to operate relay 330 as before, so that the test switch is advanced to its 22nd position. Indicating lamp 551 now lights and relays 357 and 364 are cle-energized and accordingly the current is reversed to its original direction over the junction line and the ringing lead and the alternating current relay 393 are disconnected. Upon the restoration of the current flow to normal, the polarized relay in the junction relay set releases and disconnects the battery feed thereupon releasing relay 385. The following circuit is now completed: earth, armature 392 and its front contact, armature 388 and its back contact, lead 445, 22nd contact in the bank of wiper 504 and said wiper, interrupter springs 508, lead 441, back contact and armature 313, lead 439, Winding of magnet 507 to battery. Accordingly the test switch is advanced to its 23rd position, in which position the earth on wiper 503 is extended over lead 457 to short-circuit relay 352 and this after a slight interval releases and at armature 354 disconnects the battery feed through relay 389. Since the line relay of the unction relay set is in series with relay 389, it will also restore at this time and open the junction lamp circuit so that relay 376 should also now restore. Moreover the earth on wiper 501 is now extended to the indicating lamp 541 to indicate the particular test in progress and in parallel to the winding of relay 518. This relay operates and at armature 520 opens the homing circuit of the release timing switch RS and at armature 519 connects up pulses from the interrupter 537 to the two-step relay 515.

Upon the receipt of the first pulse relay 515 operates its light armature 517 and thus prepares a locking circuit for itself which extends over the multipled contacts in the bank of wiper 512 and said wiper and lead 455 to the release trunk conductor 481 extending from the selector level. On the termination of the pulse, the lower winding of relay 515 is no longer short-circuited and the relay operates fully, thereupon at armature 516 transferring the pulsing circuit to the magnet 513 of the switch RS. This accordingly commences to step and earth is now extended in turn over wiper 509 to the supervisory lamps 552-555 indicating the length of the release interval. As soon as the release trunk conductor becomes unguarded owing to the removal of earth, the locking circuit of relay 515 is opened and it releases, thus stopping the movement of the switch. The permissible time of release is represented by the switch RS stopping on any one of contacts 9, 10 and 11 in which case the circuit of the associated supervisory lamp 554 is completed direct to battery. In case, however, the switch should come to rest either before or after reaching these positions, the associated supervisory lamps 552, 553 and 555 receive their battery over lead 476 through the winding of relay 314 and this operates to initiate the alarm in the usual manner. Furthermore if the switch RS comes to rest before reaching position 9, there will be no circuit completed for advancing the test switch. In case however there is still earth on conductor 481 when wiper 510 reaches the 9th contact in its bank, a circuit is completed from the guarding earth on lead 481, armature 373 and its back contact, lead 466, wiper 510 and the 9th contact in its bank, lead 473, armature 381 and its back contact, lead 472, 23rd contact in the bank of wiper 502 to the winding of relay 330 as previously traced. It this earth is removed While the switch RS is rotating over contacts 9, 10 and 11, the circuit of relay 330 is opened and it brings about the stepping of the test switch in the usual manner. ly, if wiper 510 passes clear of the wired contacts, the circuit of relay 330 is again opened and the test switch is stepped. Thereupon the circuit of relay 518 is opened by wiper 501 and the relay releases and at armature 520 completes the homing circuit of the switch RS by way of interrupter contacts 514. The release timing switch is thus restored to normal in readiness for the release test on the next junction. Since the last two contacts in the bank of the homing wiper 506 of the switch TS are permanently connected to earth, this switch now returns to its normal position and relay 127 is again operated. The test switch is now operated in the manner previously described and earth through the interrupter 485 is connected over lead 453 to the first two contacts in the bank of wiper Similar- 502. Consequentlyvtesting' for a free junction now recommences in the manner previously described and when such a junction is found the tests are carried out on it in the same way. l/Vhen all the junctions accessible over the junction distributor J D1 "have been either tested or found busy, the unction distributor JD2 is brought into use a'nd tests are made on the junctions accessible from its bank. lVhen these have all been dealt with, another idle position is seized-and the junctions associated therewith are routined.

v Consideration may now be given'to certain special features concerned with the operation of the routiner. It will sometimes occur that whilea position is being routined the operator returns to it and in this case it is clearly important that the routiner shall not interfere with the normal handling of calls at this position. It is therefore apparent from the fact that all the junction distributors are multipled together that no junction distributor may be left standing in engagement with Va particular junction while some other 'junction is being routined. Hence if the operator returns to the position, the junction distributor wipers must be moved clear as soon as possible. If they move to the 24th contacts, the position will be markedk as completely routined when in fact it was not, while if they are moved to the norma-l position the whole routine'test has to be done again. It is conceivable that this might happen several times and consequently that the routiner would test certain Vjunct-ions La number of times and this would delay the routining of other operators positions. To meet this possible difficulty a so-called routine suspense feature has been introduced in the present arrangement according to which if the operator takes up the position again Vwhile it is being routined the routiningV operation is held up for a certain period, for instance 3 minutes, and if the operator should vacate the position again during this period the routining is continued from the point at which it was stopped. In case, however, the position is still busy at theV` end of the time interval, the routiner is advanced to the next position and the position lpartly tested is tested again from the beginning at the neXt oppor- 'tunity.v Upon the operation of relay 131 when a free position is connected with, a circuit is completed for relay 109 asfollows: earth, armature 123 and kits front contact, back contact and armature 169, armature 134 and its front contact, winding of relay109 to battery. Relay 109 thereupon at armatures 110 and 111 prepares'circuits for the two-step relay 101, whereby earth from the Vnormally closed contacts of the operatorsbattery kfeed relay is now connected over lead 24, armature 106 and its back contact, armature 110 and its front contact, upper winding of relay 101 to battery, whereupon relay 101 operates its light armature 104 thereby connecting its lowerwinding to earth at armature 111. If the position remains free throughout the test, n-o further changes take place and the relays 101 and 109 are returned to normal when relay 131 de-energizes on the completion of the test of the position. If however the operatorshould insert her plug during the test, earth would be removed from lead 24 and, accordingly, the lower winding of relay 101 would no longer be short-circuited and it would operate fully. Thereupon, at armature 1,02 it connects earth to lead 13 to light the supervisory lamp associated with' the junction withlwhich the routiner is then connected to warn the operator not to use'this junction, at armature 103 completes a circuit j for the relay 112, at armature 105 completes a locking circuit for relay 131, at armature 106` prepares a circuit for relay 258, and at armatures 107 and 108 prepares circuits for two-step relay 261. Relay 112 at armature 114 locks up over its lower winding to earth at the back contact of armature 332, and at armature'113 opens the circuit of relay 1.80 which accordingly de-energizes, thereupon at armature 184 completing ahoming circuit for the test switch so that this accordingly restores to normal. When normal position is reached relay 127 is again operated and the locking .circuit of relayr 121 is accordingly openedat armature 128, but relay121 remains operated over its initial energizing circuit. f Consider first thecase in which the operator has arrived for a -full `spell of duty.' The first complete pulse from the 3-minute interrupter 91 will 4operate relay261 overvr lead 42 and this atarmature 262 will transfer the pulse lead to relay 258, hence wheny the neXt pulse arrives, relay 258 is operated. Thereupon at armature 259 itvcompletesy a momentary additional circuit for relay 112 over lead 40 rand at armature 260 opens the locking circuit of relay 101 and completes a circuit for the lower winding of relay 251. Relay 251 operates momentarily `but since no locking ycircuit is completed for its upper windingy at this time it releases when relay 258 falls away shortly after the end of the pulse. Upon the release of relay 101 the locking earth for relay 131 is removed and this releases, but relay 152 is locked up for the present. Accordingly the following circuit is now completed for homing the junctact, lead 20, wiper 613 of the distributor SDI, magnet 631 to battery through relay 233 asusuaL` V'Accordingly JDl is advanced and when it reaches its 24th position, relays 172 and 175 are operated to connect up the magnet of the distributor JD2. lVhen this reaches its 23rd position, relay 166 is energized and a circuit is then completed from earth, normally closed left-hand contacts of the quick routine key QR, front contact and armature 168, lead 680, armature 177 and its front contact, lead 681, back contact and armature 132, lead 49, winding of relay 270 to battery. Relay 270 now operates, at armature 273 locks up independent of relay 175, at armature 271 opens the circuit of the secdndary distributors and at armature 272 prepares a circuit for the magnet of the junction distributor JDZ. Relay 166 opens the locking circuit of relay 175 as usual and when the latter releases, the switch .TD2 is advanced to 24th position. Thereupon relay 166 is de-energized and when it releases, a circuit is completed over back contact and armature 171 for advancing the switch JD2 to 25th or normal position. This circuit is opened at armature 272 when relay 270 releases owing to the opening of its circuit at armature 168 and .TD2 is thus restored to normal. Moreover since relay 270 has now released armature 271 and relay 152 has released armature 153, the circuit for the secondary distributors is again completed and an idle position is hunted for in the usual manner. The position which the operator has taken up is now marked as untested and is fully routined when next it becomes free.

Consider now the case in which the operator again vacates the position before relay 258 has been operated from interrupter 91. lVhen the operator withdraws her plug, earth is again connected to lead 24 and is extended over armature 106 and its front contact and lead 41 to relay 258, which operates with the results previously described. In this case however when relay 101 cle-energizes, relay 131 is maintained operated by earth on lead 24 and hence no circuit is completed for homing the junction distributors. Moreover, as relay 131 is operated a locking circuit is completed for the upper winding of relay 251 extending as follows: battery, upper winding of relay 251, front contact and armature 253, armature 256 and its back contact, lead 37, front contact and armature 135, armature 129 and its front contact, front Contact and armature 13e-l, armature 169 and its back contact, front contact and armature 123 to earth. Relay 180 is operated again as soon as relay 112 de-energiZes and then prepares the test switch for further operation. Relay 251 in addition to completing a locking circuit for itself at armature 253, at armature 254 opens a point in the locking circuit of relay 330, and at armature 252 extends earth from armature 1811 over lead 426 to wiper 504 and thence to magnet 507 of the test switch by way of its interrupter contacts 508. The test switch is thus advanced to position 4, in which battery through magnet 507 is extended over wiper 50a and the fourth contact in its bank and lead 428 to earth through relay 255. Magnet 507 does not now operate but relay 255 does and at armatures 256 and 257 brings down relay 251 thus permitting the normal test operation to start on the trunk which the routiner was engaging when is operation was interrupted. This arrangement therefore ensures that each position shall be fully tested but tends to prevent certain junctions of one position being tested a number of times and thus delay in the testing of other positions.

The routine indicating key RIK is provided to enable a ready indication to be obtained of the number of positions which have been dealtwith. It will be seen that when this key is operated battery is connected to lead 14 in place of the normal earth and is extended through the various position indicating lamps to the 24th contacts in the banks of wi pers such as 636 of the various second junction distributors. In case the positions have been dealt with, these wipers Will be standing on the 21th contact and thus an earth will be supplied for lighting the lamps. As already mentioned, the indicating lamp associated with the position which is actual] being tested is normally flashed in the circuit extending from battery, back contact and armature 277, upper winding of relay 276, armature 275 and its back contact, lead 55, front contact and armature 154, lead 25, wiper 602 of the primary distributor wiper 612 of the secondary distributor SDl, lamp such as 608, lead 14. normally closed contacts of the routine indicating key RIK to earth. Hence when the key is operated, this lamp will be extinguished though this is of little importance and the lamps associated with all the positions which have already been routined, will be lighted. By this means the attendant can readily ascertain at any time the exact progress of the test.

The release alarm key RA is provided in order to enable the alarm to be disconnected after a fault has been found. It will be seen that earth is provided over the normally closed contacts of this key and lead 72 to lock up the alarm relay 309 which is operated as shortly to be described when a fault is found.

The re-start key RS enables the testing operation to be re-started after it has been stopped due to the distributors making a complete revolution without finding any positions idle and untested. At the left-hand springs of this key earth is then removed from lead 34 so as to open the locking circuit of the routine finished relay 285 while at the righthand springs a. point in the lockingr circuit of relay 152 is opened; consequently conditions are again restored for enabling the distributors to make a further test for posi- 

